libavcodec/qcelp_lsp.c File Reference

QCELP decoder. More...

#include "libavutil/mathematics.h"

Go to the source code of this file.

Defines
#define	QCELP_BANDWITH_EXPANSION_COEFF   0.9883
	initial coefficient to perform bandwidth expansion on LPC
Functions
static void	lsp2polyf (const float *lspf, double *f, int lp_half_order)
	Computes the Pa / (1 + z(-1)) or Qa / (1 - z(-1)) coefficients needed for LSP to LPC conversion.
void	ff_qcelp_lspf2lpc (const float *lspf, float *lpc)
	Reconstructs LPC coefficients from the line spectral pair frequencies and performs bandwidth expansion.

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Detailed Description

QCELP decoder.

Author:

Reynaldo H. Verdejo Pinochet

Remarks:

FFmpeg merging spearheaded by Kenan Gillet

Development mentored by Benjamin Larson

Definition in file qcelp_lsp.c.

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Define Documentation

#define QCELP_BANDWITH_EXPANSION_COEFF   0.9883

initial coefficient to perform bandwidth expansion on LPC

Note:

: 0.9883 looks like an approximation of 253/256.

TIA/EIA/IS-733 2.4.3.3.6 6

Definition at line 39 of file qcelp_lsp.c.

Referenced by ff_qcelp_lspf2lpc().

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Function Documentation

void ff_qcelp_lspf2lpc	(	const float *	lspf,
		float *	lpc
	)

Reconstructs LPC coefficients from the line spectral pair frequencies and performs bandwidth expansion.

Reconstructs LPC coefficients from the line spectral pair frequencies.

Parameters:

	lspf	line spectral pair frequencies
	lpc	linear predictive coding coefficients

Note:

: bandwith_expansion_coeff could be precalculated into a table but it seems to be slower on x86

TIA/EIA/IS-733 2.4.3.3.5

Definition at line 80 of file qcelp_lsp.c.

Referenced by interpolate_lpc().

static void lsp2polyf	(	const float *	lspf,
		double *	f,
		int	lp_half_order
	)			[static]

Computes the Pa / (1 + z(-1)) or Qa / (1 - z(-1)) coefficients needed for LSP to LPC conversion.

We only need to calculate the 6 first elements of the polynomial.

Parameters:

	lspf	line spectral pair frequencies
	f	[out] polynomial input/output as a vector

TIA/EIA/IS-733 2.4.3.3.5-1/2

Definition at line 51 of file qcelp_lsp.c.

Referenced by ff_qcelp_lspf2lpc().